Tail of mortar projectile



April was H. o. DONNER 3,085,511

TAIL. 0F MORTAR PROJECTILE Filed April 22, 1959 INVENTOR. HANS a DONNER 3,085,511 TAR. 6F MORTAR ERBJECTILE Elms t). Donner, Hameenlratu 14, Tampere, Finland Filed Apr. 22, 1959, Ser. No. 888,995 Claims. (ill. 1825ti) The invention relates to an improvement in the tail fins of a mortar projectile.

In order to stabilize a projectile in flight, there are provided radially extending tail fins usually fitted at the rear end of the projectile.

Known tail vanes are usually either straight edged or taper outwards. It is important to have tail vanes in order that the projectile be well guided and as stable as possible in its trajectory in order to achieve good target accuracy. This can be realized by increasing the size of the tail vanes or by increasing their number, but this causes other diificulties, such as increasing the weight of the tail part, which may prove disadvantageous.

It is an object of this invention to provide an effective set of tail vanes without any increase in the area of the vanes or in their number.

A tail vane according to the present invention is characterized in that the leading edge of the vane, preferably at a point halfway of the height of the vane, has a tooth or discontinuous jump whereby the tail vane is Wider radially outwards of the rnidheight of the vane, said tooth causing a deflection of the air current and turning and condensing of the current against the outer part of the tail vane, thus improving the stabilizing properties of the vane.

A tail vane according to the present invention is more closely described in the following description, with reference to the attached drawing and without restricting the invention in any way particularly to this construction.

The attached drawing is a side view, partly in section, of the rear of a mortar projectile showing tail fins according to this invention.

Part 1 is the rear part of the body of the projectile, radially extending tail fins 2 are coupled to the body 1. The tail fins may be suitably formed of drawn light-alloy sections.

In accordance with the invention, the tail fins are so shaped that at a point halfway of the height of the fin there is a tooth 3 extending in a direction parallel to the axis of the body 1 such that the longitudinal extent of the tail fin radially outwards of the tooth 3 is greater than the longitudinal extent of the fin radially inwards of the tooth 3. The leading edges of the tail fins therefore each have a discontinuous jump at tooth 3. Additionally, the leading edge portion of each fin inwardly of the tooth 3 is parallel to the leading edge portionoutboardly of the tooth 3. At the root of the tooth there may also be provided a narrow crack 4 for assisting the deflection of the air current even further and for improving the stability properties of the vane. Crack 4 extends in the fin a small distance in the longitudinal ice 2 direction of the projectile. In the drawing it is designated with a dash line.

The invention can, of course, have also other embodiments without departing from the scope of the following claims.

What is claimed is:

1. A mortar projectile comprising an elongated body having a longitudinal axis, tail fins on said body extending radially therefrom to define fins of determinable height, each tail fin including a leading edge, said leading edge extending from said body in rearwardly inclined manner to a location substantially midway of the height of the corresponding fin, said leading edge having a discontinuous jump at the aforenoted location whereat the leading edge extends forwardly and parallel to the longitudinal axis, said leading edge extending radially outward from said discontinuous jump in rearwardly inclined direction and substantially parallel to the leading edge between the body and the discontinuous jump.

2. A mortar projectile comprising an elongated body having a longitudinal axis, and tail fins on and extending radially from said body, said tail fins having a longitudinal extent, each tail fin having a leading edge inclined towards the rear of the body and each leading edge being provided with a discontinuous jump such that the fin has a longitudinal extent radially outwards of said discontinuous jump which is greater than the longitudinal extent radially inwards of said discontinuous jump, the leading edge inwards and outwards of said discontinuous jump extending parallel to one another.

3. A projectile as claimed in claim 2 wherein said leading edge has a saw tooth shape.

24. A projectile as claimed in claim 3 wherein each fin is further provided with a narrow longitudinally extending crack at said discontinuous jump.

5. A mortar projectile comprising an elongated body having a longitudinal axis, and tail fins on and extending radially from said body, each of said tail fins including a leading edge, said leading edge being constituted by first and second portions extending parallel to one another and a third portion connecting said first and second portions and extending parallel to said axis to form a discontinuous jump such that the longitudinal extent of the tail fin radially outwards of said third portion is greater than the longitudinal extent of the tail fin radially inwards of said third portion.

References Cited in the file of this patent UNITED STATES PATENTS 2,427,217 Lebherz et al. Sept. 9, 1947 2,494,026 Anderson Ian. 10, 1950 2,581,884 Ringel Jan. 8, 1952 2,724,237 Hickman Nov. 22, 1955 2,759,326 Brandt Aug. 21, 1956 2,784,669 Apotheloz et al. Mar. 12, 1957 2,899,773 Lockwood A Aug. 18, 1959 

2. A MORTAR PROJECTILE COMPRISING AN ELONGATED BODY HAVING A LONGITUDINAL AXIS, AND TAIL FINS ON AND EXTENDING RADIALLY FROM SAID BODY, SAID TAIL FINS HAVING A LONGITUDINAL EXTENT, EACH TAIL FIN HAVING A LEADING EDGE INCLINED TOWARDS THE REAR OF THE BODY AND EACH LEADING EDGE BEING PROVIDED WITH A DISCONTINUOUS JUMP SUCH THAT THE FIN HAS A LONGITUDINAL EXTENT RADIALLY OUTWARDS OF SAID DISCONTINUOUS JUMP WHICH IS GREATER THAN THE LONGITUDINAL EXTENT RADIALLY INWARDS OF SAID DISCONTINUOUS JUMP, THE LEADING EDGE INWARDS AND OUTWARDS OF SAID DISCONTINUOUS JUMP EXTENDING PARALLEL TO ONE ANOTHER. 